Release Notes

9 Dell PS Series: Space Borrowing for Snapshots and Replicas | TR1084 | version 2
1.2.1 Replication Space
Volume replication between partners requires space on both the primary group (the volume location) and the
secondary group (the replica location). These space requirements are classified as follows:
Delegated space on the secondary group, is the amount of space dedicated to storing replicas from the primary group.
All replica reserves are confined to exist within this configured limit.
Local replication reserve on the primary group, is the amount of space reserved in the pool for replication operations.
Current replica volume reserve (in MB/GB/TB) on the secondary group, is the reserved space for replication on the
volume.
Total replica reserve is the amount of space reserved for the replica set within the configured delegated space on the
secondary group. Total replica reserve is a percentage of the current replica volume reserve that provides additional
space for replicas. If the current replica reserve is 1 GB, and you specify 200% for total replica reserve, the total replica
reserve size is 2 GB. If the current replica volume reserve increases to 4 GB, then the total replica reserve size also
increases to 8 GB. The total replica reserve for a volume can potentially limit the number of replicas that are kept. To
prevent older replicas from being deleted, space can automatically be borrowed from other sources when the total
replica reserve is consumed.
Figure 1 Examples of group space usage
For additional information on using Asynchronous Replication with Dell PS Series, refer to:
• Dell EqualLogic Group Manager Administrator’s Manual on eqlsupport.dell.com (login required)
• Using Dell PS Series Asynchronous Replication